Method and apparatus of primary cell indication for enhanced control channel demodulation

ABSTRACT

Method and apparatus of primary cell indication for enhanced control channel demodulation method and apparatus are disclosed. Control information receiving method in a multi-distributed node system includes demodulating a first cell identification (ID) based on a synchronization signal (SS), demodulating information indicating a second cell ID based on a radio resource control (RRC) message and demodulating enhanced physical downlink control channel (e-PDCCH) based on the second cell ID, Accordingly, it may be possible to reduce complexity that occurs when the optimal prediction motion vector is induced and to enhance efficiency.

This application is the National Phase of PCT/KR2012/008303 filed onOct. 12, 2012, which claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application No. 61/548,233 filed on Oct. 18, 2011, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

TECHNICAL FIELD

The present invention relates to wireless communication, and morespecifically to a method and apparatus for demodulating controlinformation.

BACKGROUND ART

More and more data is recently transmitted over a wireless communicationnetwork due to appearance of various devices, such as smartphones ortablet PCs, which require machine-to-machine (M2M) communication andtransmission of a large amount of data. More interest is oriented towardcarrier aggregation and cognitive radio technologies that enableeffective use of a broader frequency bandwidth to satisfy transmissionof a large amount of data and multi-antenna technologies and multi-basestation cooperative technologies that may raise data capacity in alimited frequency range.

Further, wireless communication networks have been evolving in such amanner that the density of nodes to which a user may gain accessincreases. Here, the “nodes” occasionally mean antennas or antennagroups which are spaced apart at a predetermined distance in adistributed antenna system (DAS), but are not limited to such concept,and may be expanded in meaning. That is, a node may be a pico-cell basestation (PeNB), a home base station (HeNB), an RRH (remote radio head),an RRU (remote radio unit), or a relay. When having higher density ofnodes, the wireless communication system may show higher systemperformance thanks to inter-node cooperation.

In other words, rather than when operating as an independent basestation (Base Station (BS), Advanced BS (ABS), Node-B (NB), eNode-B(eNB), Access Point (AP), etc.) without cooperation from another node,when the transmission/reception is managed by a control station tothereby operate as an antenna or antenna group in a cell, each node mayexhibit much higher system performance. Hereinafter, a wirelesscommunication system including a plurality of nodes is referred to asmulti-node system.

Not only when defined as an antenna group having a predeterminedinterval, but also when defined as an antenna group that has nothing todo with the interval, the nodes may apply. For example, it can be seenthat a base station including Gloss polarized antennas is constituted ofa node having an H-pol antenna and a node having a V-pol antenna.

In the multi-node system, different nodes from each other for eachterminal may transmit a signal to the terminal, and a plurality of nodesmay be set. At this time, different reference signals for each node maybe transmitted. In such case, the terminal may measure a channel statebetween each node and the terminal based on the plurality of referencesignals and may periodically or aperiodically feed back channel stateinformation.

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a method ofdemodulating control information using a cell ID (identification).

Another object of the present invention is to provide an apparatus thatperforms a method of demodulating control information using a cell ID(identification).

Solution to Problem

To achieve the above objects, according to an aspect of the presentinvention, a method for receiving control information in amulti-distributed node system may include demodulating a first cellidentification (ID) based on a synchronization signal (SS), demodulatinginformation indicating a second cell ID based on a radio resourcecontrol (RRC) message and demodulating enhanced physical downlinkcontrol channel (e-PDCCH) based on the second cell ID, wherein the firstcell ID is an indication shared by a plurality of neighboring nodes andwherein the second cell ID is an indication identifying the plurality ofneighboring nodes. The information indicating the second cell ID may beincluded in configuration information of the e-PDCCH. The demodulatinginformation indicating the second cell ID may include demodulating acell ID of a received channel state information (CSI)-reference signal(RS) based on the RRC message, demodulating a primary physical cell ID(PPCI) indication of the CSI-RS based on the RRC message and setting thesecond cell ID equal to the cell ID of the CSI-RS, wherein the cell IDof CSI-RS indicates a node transmitting the CSI-RS and wherein the PPCIindication indicates whether the second cell ID is equal to the cell IDof the CSI-RS. The method for receiving control information in amulti-distributed node system may further include demodulating physicaldownlink shared channel (PDSCH) based on the CSI-RS, wherein the PDSCHis generated with a cell ID same as the cell ID of the CSI-RS. Thedemodulating information indicating the second cell ID may includedemodulating a cell ID of a CSI-RS located predetermined resourceelement based on the RRC message and setting the second cell ID equal tothe cell ID of the CSI-RS, wherein the cell ID of the CSI-RS indicates anode transmitting the CSI-RS. The method for receiving controlinformation in a multi-distributed node system may further includedemodulating physical downlink shared channel (PDSCH) based on theCSI-RS, wherein the PDSCH is generated with a cell ID same as the cellID of the CSI-RS.

To achieve the above objects, according to an aspect of the presentinvention, a wireless device configured to receive control informationin a multi-distributed node system, the wireless device may include aprocessor configured to demodulate a first cell identification (ID)based on a synchronization signal (SS) and demodulate informationindicating a second cell ID based on a radio resource control (RRC)message and a transceiver configured to demodulate enhanced physicaldownlink control channel (e-PDCCH) based on the second cell ID, whereinthe first cell ID is a indication shared by a plurality of neighboringnodes and wherein the second cell ID is a indication identifying theplurality of neighboring nodes. The information indicating the secondcell ID may be included in configuration information of the e-PDCCH. Theprocessor may further configured to demodulate information indicatingthe second cell ID by demodulating a cell ID of a received channel stateinformation (CSI)-reference signal (RS) based on the RRC message anddemodulating a primary physical cell ID (PPCI) indication of the CSI-RSbased on the RRC message; and setting the second cell ID equal to thecell ID of the CSI-RS, wherein the cell ID of the CSI-RS indicates anode transmitting the CSI-RS and wherein the PPCI indication indicateswhether the second cell ID is equal to the cell ID of the CSI-RS. Theprocessor may be further configured to demodulate physical downlinkshared channel (PDSCH) based on the CSI-RS, wherein the PDSCH isgenerated with a cell ID same as the cell ID of the CSI-RS. Theprocessor may be further configured to demodulate physical downlinkshared channel (PDSCH) based on the CSI-RS, wherein the PDSCH isgenerated with a cell ID same as the cell ID of the CSI-RS. Theprocessor may be further configured to demodulate information indicatingthe second cell ID by demodulating a cell ID of a CSI-RS locatedpredetermined resource element based on the RRC message; and setting thesecond cell ID equal to the cell ID of the CSI-RS, wherein the cell IDof the CSI-RS indicates a node transmitting the CSI-RS. The processormay be further configured to demodulate physical downlink shared channel(PDSCH) based on the CSI-RS, wherein the PDSCH is generated with a cellID same as the cell ID of the CSI-RS.

Advantageous Effects of Invention

As described above, the control channel demodulating method andapparatus using a primary cell ID according to an embodiment of thepresent invention may receive control information transmitted from atleast one node having a same virtual cell ID as the primary cell ID.Accordingly, a wireless device may receive the control informationselectively in distributed node system using the virtual cell ID and theprimary cell ID.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual view illustrating a single cell multi-distributednode system.

FIG. 2 is a conceptual view illustrating the transmission of the CSI-RSand the feedback of CSI measured by a terminal.

FIG. 3 is a conceptual view illustrating the position of CSI-RSs in aresource block pair according to the number of the CSI-RSs.

FIG. 4 is a conceptual view illustrating a plurality of structures whereCSI-RSs are mapped in the resource block pair.

FIG. 5 is a conceptual view illustrating a data transmission methodusing CoMP (coordinated multipoint transmission).

FIG. 6 is a conceptual view illustrating a newly introduced controlchannel, e-PDCCH (enhanced physical downlink control channel).

FIG. 7 is a conceptual view illustrating a relay scheme suggested inLTE.

FIG. 8 is a conceptual view illustrating a structure of allocation of anR-PDCCH for a relay.

FIGS. 9 and 10 are conceptual views illustrating methods of assigninge-PDCCH in the subframe.

FIG. 11 is a conceptual view illustrating the nested virtual cellsystem.

FIG. 12 is a conceptual view illustrating a method of transmitting avirtual cell ID through a CSI-RS information element according to anembodiment of the present invention.

FIG. 13 is a conceptual view illustrating a method of transmittingvirtual cell ID information that transmits e-PDCCH according to anembodiment of the present invention.

FIG. 14 is a conceptual view illustrating a method of allowing aterminal to implicitly estimate information on a virtual cell IDaccording to an embodiment of the present invention.

FIG. 15 is a conceptual view illustrating a method of controlling theoperation of a node using PPCI according to an embodiment of the presentinvention.

FIG. 16 is a block diagram illustrating a wireless apparatus accordingto an embodiment of the present invention.

MODE FOR THE INVENTION

The following technologies may be used in various multiple accessschemes, such as CDMA (code division multiple access), FDMA (frequencydivision multiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), or SC-FDMA (singlecarrier-frequency division multiple access).

CDMA may be implemented as a radio technology, such as UTRA (UniversalTerrestrial Radio Access) or CDMA2000. TDMA may be implemented as aradio technology, such as GSM (Global System for Mobilecommunications)/GPRS (General Packet Radio Service)/EDGE (Enhanced DataRates for GSM Evolution). OFDMA may be implemented as a radiotechnology, such as IEEE (Institute of Electrical and ElectronicsEngineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or EUTRA(Evolved UTRA). UTRA is part of UMTS (Universal MobileTelecommunications System). 3GPP (3rd Generation Partnership Project)LTE (Long Term Evolution) is part of E-UMTS (Evolved UMTS) using E-UTRA,and adopts OFDMA for downlink and SC-FDMA for uplink. LTE-A (Advanced)is an evolution of LTE.

FIG. 1 is a conceptual view illustrating a single cell multi-distributednode system.

Referring to FIG. 1, in the single cell multi-distributed node system,the transmission/reception of each node 110, 120, 130, 140, 150, and 160is managed by a single base station controller 100 and so may operate aspart of one cell.

Hereinafter, in an embodiment of the present invention, a node generallyrefers to an antenna group (which may physically correspond to RRH(Remote Radio Head) or RRU (Remote Radio Unit)) spaced apart by apredetermined interval or more from a DAS (Distributed Antenna System).However, as used herein, the node may be construed as some antenna groupirrespective of a physical interval. For example, according to anembodiment of the present invention, a base station consisting of crosspolarized antennas may be referred to as being constituted of a nodeincluding an H-pol antenna and a node including a V-pol antenna. A nodemay be not an antenna group, but a base station, such as a pico-cellbase station (PeNB) or a home base station (HeNB).

Further, as used herein, the ‘node’ is not restricted to a node in thephysical point of view and may be expanded as a node in the logicalpoint of view. The ‘node in the logical point of view’ means atransmission pilot signal that is recognized as a node by a terminal.For example, an LTE terminal may recognize configuration information ofa node through CRS (Cell-specific Reference Signal) or CSI-RS (ChannelState Information Reference Signal) port(s). Accordingly, a nodelogically recognized by a terminal may be different from an actualphysical node. For example, in a cell where N CRS ports are transmitted,an LTE terminal may recognize that this cell is constituted of one nodehaving N transmission antennas. However, this cell may have variousphysical node configurations. For example, in the cell, two nodes eachmay transmit N/2 CRS ports. As another example, a number of nodes havingN transmission antennas may transmit CRS ports in an SFN (SingleFrequency Network) style.

At last, the relationship between a physical node and a logical node maybe transparent in light of a terminal, and the terminal may thusrecognize the node in the logical point of view and may performtransmission/reception processing. In an LTE-A system, a logical nodemay be recognized as one CSI-RS resource (or pattern). For example, if anumber of CSI-RS resources are set for a terminal, the terminal mayrecognize each CSI-RS resource as one logical node and may performtransmission/reception processing.

Hereinafter, an antenna according to an embodiment of the presentinvention may be also referred to as an antenna port, a virtual antenna,or antenna group, as well as a physical antenna.

In a multi-distributed multi-node system, a terminal should performcoherent demodulation on various downlink physical channels. For theterminal to perform coherent demodulation, downlink channel estimationis needed. The terminal may estimate the downlink channel by inserting areference symbol known to the terminal into an OFDM time-frequency grid(or resource grid). Such reference symbol may be referred to as‘downlink reference symbol’ or ‘reference symbol’. The followingreference symbols may be used:

(1) Cell-specific reference signal (CRS) may be transmitted over eachdownlink subframe and all resource blocks and may cover all cellbandwidths. In case a transmission mode is 7, 8, or 9, the CRS may beused as a reference signal for coherent demodulation of a signaltransmitted through physical channels other than a PMCH (physicalmulticast channel) and a PDSCH (physical downlink shared channel). Thesituation where the transmission mode is 7, 8 or 9 refers to whennon-codebook-based precoding is done.

Further, the CRS may be used for the terminal to obtain CSI(Channel-State Information), and the terminal may select a cell and maydetermine whether handover is performed based on the CRS.

(2) Demodulation reference signal (DM-RS) may be also defined asUE-specific reference signal. In case the transmission mode is 7, 8 or9, the DM-RS may be used for the terminal to perform channel measurementon a PDSCH (Physical Downlink Shared Channel). The term “UE-specific”means that each demodulation reference signal (DM-RS) is used forchannel measurement by a single terminal. That is, the DM-RS may betransmitted through a resource block transmitted to a specific terminalthrough the PDSCH.

(3) CSI reference signal (CSI-RS) refers to a reference signal used toobtain channel-state information (CSI). The CSI-RS has very lowtime/frequency density and so has a low overhead compared to theabove-described CRS.

(4) MBSFN reference signal is used for channel measurement for coherentdemodulation upon transmission of an MCH (multicast channel) using anMBSFN (multicast-broadcast single frequency network)

(5) Positioning reference signal is a reference signal used forenhancing LTE positioning functionality. This reference signal may beused to perform terminal measurement in a plurality of LTE cells so asto measure the geographical position of the terminal. In a specificcell, the positioning reference signal may be used at a position of anempty resource element in an adjacent cell so that a high SIR (Signal toInterference Ratio) may be obtained.

Hereinafter, according to an embodiment of the present invention, amethod of performing channel estimation using the CSI-RS in a multi-nodedistributed system is described.

FIG. 2 is a conceptual view illustrating the transmission of the CSI-RSand the feedback of CSI measured by a terminal.

Referring to FIG. 2, a receiver 210 may feed channel informationproduced based on the CSI-RS transmitted from a transmitter 200 back tothe transmitter 200 based on parameters, such as RI (rank index), PMI(precoding matrix index), and CQI (channel quality indicator). Theparameters, such as RI, PMI, and CQI, which indicate channelinformation, may be referred to as CSI (channel state information).

(1) RI (rank index) provides recommendation for a transmission rank tobe used to the transmitter 200. That is, the RI may provide informationon the number of layers used for downlink transmission to thetransmitter 200.

(2) PMI (precoding matrix index) may be used as a value that indicates aprecoder matrix used for downlink transmission. The precoder matrix maybe determined by estimating the number of layers indicated by the RI.

(3) CQI (channel-quality indication) may provide information on thehighest modulation coding scheme to the transmitter 200.

As the feedback information of the CSI-RS transmitted from thetransmitter 200, the receiver 210 may transmit RI, PMI, and CQI, whichare information indicating the channel state, to the transmitter 200,thereby reporting the channel state.

Since the above-described CRS is also a reference signal that may beused to obtain the channel state information, the CRS and the CSI-RS mayoverlap in responsibility. The CSI-RS may be used to back up the CRSthat is a preexisting reference signal for the following two reasons:

(1) In LTE release 8, up to four reference signal might be provided forone cell. However, in LTE release 10, one base station supports eighttransmission antennas, and thus, downlink spatial multiplexing ispossible for up to 8 layers. For such reason, rather than the CRS thatis a reference signal that has been already used in LTE release 8, theCSI-RS may be used as a reference signal for expanding CSI capability.

(2) The time-frequency density of the existing CRS is high because itwas set to be able to perform channel measurement in the circumstancewhere the channel changes very quickly. Accordingly, the CRS operates ashigh overhead. On the contrary, the CSI-RS is a reference signaltargeting only the CSI, and thus has low time-frequency density andprovides relatively low overhead compared to the CRS. Accordingly,rather than expanding the CRS that is an existing reference signal, theCSI-RS with low time-frequency density and low overhead may be definedand used as a new type of a reference signal.

One cell may use 1, 2, 4 or 8 CSI-RSs on a per-resource block pairbasis. The CSI-RS structure (or CSI-RS configuration) which represents astructure where CSI-RSs are arranged in a resource grid may varydepending on the number of CSI-RSs used in one cell. For example, incase one CSI-RS is used in a resource block pair, the CSI-RS may have 40different combinations.

The resource block pair is a unit of a resource, which includes tworesource blocks, and one resource block may be a unit of a resource,which includes 12 subcarriers on the frequency axis and 7 OFDM symbolson the time axis.

FIG. 3 is a conceptual view illustrating the position of CSI-RSs in aresource block pair according to the number of the CSI-RSs.

Referring to FIG. 3, the resource block pair 300 and 310 uses twoCSI-RSs. The hatched portions refer to where the CSI-RSs may bepositioned on the resource grid.

For example, two CSI-RSs 300-2-1 and 300-2-2 may be positioned on twoconsecutive reference elements in one resource block 300-2 on the timeaxis. The two CSI-RSs 300-2-1 and 300-2-2, respectively, may useorthogonal cover codes (OCCs) so that the CSI-RSs do not interferencewith each other. Two CSI-RSs may be positioned on the resource elementsmarked with hatching, and in case two CSI-RSs are used in one resourceblock pair, two combinations may be present in the resource block pair.

Referring back to FIG. 3, 1) an example where four CSI-RSs are used inone resource block pair 340 or 345 and 2) an example where eight CSI-RSsare used in one resource block pair 360 or 365 are shown.

In case four CSI-RSs are used, 10 different CSI-RS structurecombinations may be present in the resource block pair, and in caseeight CSI-RSs are used, five different CSI-RS structure combinations maybe present in the resource block pair.

In case one CSI-RS is used in the resource block pair, the same CSI-RSstructure as when two CSI-RSs are used may be provided like the resourcepair block 300 and 310 shown in FIG. 1.

In light of time domain, a period at which the CSI-RS is transmitted maybe various from 5 ms (every fifth subframe) to 80 ms (every eighthframe). In case one CSI-RS is transmitted every 5 ms, the overhead thatoccurs because the CSI-RS is used may be 0.12%. To avoid interferencewith an adjacent cell, a subframe where the CSI-RS may be made to have adifferent value from that of the adjacent cell even in the time domain.

Although in FIG. 3 the CSI-RS is transmitted on one resource block inthe frequency domain, the CSI-RS may be transmitted on all the resourceblocks in the frequency domain, so that the CSI-RS may be transmittedthrough all the cell bandwidths.

Turning back to FIG. 3, as described above, the CSI-RS may be also usedat the position of a resource element different from the currentposition of the CSI-RS. Among resource elements that correspond topotential positions of the CSI-RS, a resource element that is not usedfor the CSI-RS may be used for transmission of data symbols.

However, as another method, a resource element corresponding to apotential CSI-RS position may be used as a muted CSI-RS (or zero powerCSI-RS). The muted CSI-RS is the same as a general CSI-RS structure butdiffers from the general CSI-RS structure in that nothing is transmittedat the position of the corresponding resource element.

In case a CSI-RS is transmitted from an adjacent cell, the muted CSI-RSof the current cell may be a “transmission hole”, which may be used forthe following two purposes:

(1) Enables a terminal to receive a CSI-RS of an adjacent cell withoutbeing influenced by transmission from its cell. The channel informationmay be obtained by receiving the CSI-RS of the adjacent cell. Thechannel information based on the CSI-RS of the adjacent cell may beutilized in a multi-cell transmission technology, such as CoMP(cooperative multipoint).

(2) Reduces interference to CSI-RS transmission in another cell. In anetwork, such as a heterogeneous network, where cells overlap eachother, energy may be removed from the position of a resource elementwhere a CSI-RS is transmitted from the other cell, so that a signal fromthe other cell may be prevented from being interfered by a signaltransmitted from the current cell.

As in case (1), upon receiving a CSI-RS of the adjacent cell, since amuted CSI-RS is used for the CSI-RS aggregation used in the adjacentcell, a muted CSI-RS constituted of a plurality of aggregations may beused. A muted CSI-RS including one aggregation may be used to avoidinterference with a CSI-RS of a cell overlapping its own cell as in case(2).

FIG. 4 is a conceptual view illustrating a plurality of structures whereCSI-RSs are mapped in the resource block pair.

In the following embodiment, for ease of description, two CSI-RSs areassumed to be included in the resource block pair, but as describedabove, one, four, or eight CSI-RSs may be included in the resource blockpair.

Referring to FIG. 4, to reduce inter-cell interference in a multi-cellenvironment, such as HetNet, a CSI-RS may have different configurations(or structures) in the resource block pair.

In the resource block pair, the CSI-RS configuration may vary dependingon the number of antenna ports in the cell, and as different CSI-RSconfiguration as possible may be made between adjacent cells.

Further, in the resource block pair, the CSI-RS configurations may bedivided depending on the type of CP (cyclic prefix), and may also beseparated into a case of applying to both frame structure 1 and framestructure 2 and a case of applying only to frame structure 2 (framestructure 1 and frame structure 2 indicate whether the transmissionscheme is TDD (time division duplex) or FDD (frequency division duplex).

Further, the CSI-RS supports up to 8 ports

(p=15,

p=15,16,

p=15, . . . , 18

and

p=15, . . . , 22)

contrary to the CRS and may be defined for

Δf=15 kHz.

The CSI-RS configuration may be produced by the following method.

A sequence for the CSI-RS,

r_(l,n) _(s) (m),

is generated by the following equation:

$\begin{matrix}{{{{r_{l,n_{S}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\;\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},\mspace{79mu}{m = 0},1,\ldots\mspace{14mu},{N_{RB}^{\max,{DL}} - 1}}\mspace{79mu}{{where},{c_{init} = {{2^{10} \cdot \left( {{7 \cdot \left( {n_{s} + 1} \right)} + l + 1} \right) \cdot \left( {{2 \cdot N_{ID}^{cell}} + 1} \right)} + {2 \cdot N_{ID}^{cell}} + N_{CP}}}}\mspace{79mu}{N_{CP} = \left\{ \begin{matrix}1 & {{for}\mspace{14mu}{normal}\mspace{14mu} C\; P} \\0 & {{for}\mspace{14mu}{extended}\mspace{14mu} C\; P}\end{matrix} \right.}} & \left\langle {{Equation}\mspace{14mu} 1} \right\rangle\end{matrix}$

In the above equation,

n_(s)

refers to a slot number in one radio frame, and

l

refers to an OFDM symbol number in the slot.

c(i)

refers to a pseudo random sequence, and starts from each OFDM symbol as

C_(init).

N_(ID) ^(cell)

refers to a physical layer cell ID.

The pseudo-random sequence,

r_(l,n) _(s) (m),

generated in a seed value based on a cell ID may be subjected toresource mapping with a complex-valued modulation symbol

α_(k,l) ^((p)).

The following Equation 2 refers to an equation in which in the subframesconfigured to transmit CSI-RSs, the reference signal sequence,

r_(l,n) _(s) (m),

is mapped with complex-valued modulation symbol

α_(k,l) ^((p)),

which is used a reference symbol for antenna port p.

$\begin{matrix}{{a_{k,l}^{(p)} = {w_{l^{''}} \cdot {r_{l,n_{s}}\left( m^{\prime} \right)}}}{where}{k = {k^{\prime} + {12m} + \left\{ {{\begin{matrix}{{{{- 0}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 6}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 1}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 7}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{- 0}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {15,16} \right\}} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 3}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {17,18} \right\}},} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 6}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {19,20} \right\}},} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{{{- 9}\mspace{14mu}{for}\mspace{14mu} p} \in \left\{ {21,22} \right\}},} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}\end{matrix}l} = {l^{\prime} + \left\{ {{\begin{matrix}{{1^{''}\mspace{14mu} C\; S\; I\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 0\text{-}19},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{21^{''}\mspace{14mu} C\; S\; I\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 20\text{-}31},} & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\{{1^{''}\mspace{14mu} C\; S\; I\mspace{14mu}{reference}\mspace{14mu}{signal}\mspace{14mu}{configurations}\mspace{14mu} 0\text{-}27},} & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}\end{matrix}w_{l^{''}}} = \left\{ {{{\begin{matrix}1 & {p \in \left\{ {15,17,19,21} \right\}} \\\left( {- 1} \right)^{1^{''}} & {p \in \left\{ {16,18,20,22} \right\}}\end{matrix}l^{''}} = 0},{{1m} = 0},1,\ldots\mspace{14mu},{{N_{RB}^{DL} - {1m^{\prime}}} = {m + \left\lfloor \frac{N_{RB}^{\max,{DL}} - N_{RB}^{DL}}{2} \right\rfloor}}} \right.} \right.}} \right.}}} & \left\langle {{Equation}\mspace{14mu} 2} \right\rangle\end{matrix}$

In Equation 2,

(k′,l′)

and

n_(s)

are given in Tables 1 and 2 which are to be described below. The CSI-RSmay be transmitted through a downlink slot that satisfies the conditionsgiven in Tables 1 and 2.

The following Table 1 represents the CSI-RS settings for a normal CP.

TABLE 1 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 configuration (k′, l′) ns mod2 (k′, l′) ns mod2 (k′, l′) nsmod2 frame 0 (9, 5) 0 (9, 5) 0 (9, 5) 0 structure 1 (11, 2)  1 (11, 2) 1 (11, 2)  1 type 1 2 (9, 2) 1 (9, 2) 1 (9, 2) 1 and 2 3 (7, 2) 1 (7, 2)1 (7, 2) 1 4 (9, 5) 1 (9, 5) 1 (9, 5) 1 5 (8, 5) 0 (8, 5) 0 6 (10, 2)  1(10, 2)  1 7 (8, 2) 1 (8, 2) 1 8 (6, 2) 1 (6, 2) 1 9 (8, 5) 1 (8, 5) 110 (3, 5) 0 11 (2, 5) 0 12 (5, 2) 1 13 (4, 2) 1 14 (3, 2) 1 15 (2, 2) 116 (1, 2) 1 17 (0, 2) 1 18 (3, 5) 1 19 (2, 5) 1 frame 20 (11, 1)  1 (11,1)  1 (11, 1)  1 structure 21 (9, 1) 1 (9, 1) 1 (9, 1) 1 type 2 22(7, 1) 1 (7, 1) 1 (7, 1) 1 only 23 (10, 1)  1 (10, 1)  1 24 (8, 1) 1(8, 1) 1 25 (6, 1) 1 (6, 1) 1 26 (5, 1) 1 27 (4, 1) 1 28 (3, 1) 1 29(2, 1) 1 30 (1, 1) 1 31 (0, 1) 1

Table 2 represents CSI-RS settings for an expanded CP.

TABLE 2 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 configuration (k′, l′) ns mod2 (k′, l′) ns mod2 (k′, l′) nsmod2 frame 0 (11, 4)  0 (11, 4)  0 (11, 4)  0 structure 1 (9, 4) 0 (9,4) 0 (9, 4) 0 type 1 2 (10, 4)  1 (10, 4)  1 (10, 4)  1 and 2 3 (9, 4) 1(9, 4) 1 (9, 4) 1 4 (5, 4) 0 (5, 4) 0 5 (3, 4) 0 (3, 4) 0 6 (4, 4) 1 (4,4) 1 7 (3, 4) 1 (3, 4) 1 8 (8, 4) 0 9 (6, 4) 0 10 (2, 4) 0 11 (0, 4) 012 (7, 4) 1 13 (6, 4) 1 14 (1, 4) 1 15 (0, 4) 1 frame 16 (11, 1)  1 (11,1)  1 (11, 1)  1 structure 18 (10, 1)  1 (10, 1)  1 (10, 1)  1 type 2 19(9, 1) 1 (9, 1) 1 (9, 1) 1 only 20 (5, 1) 1 (5, 1) 1 21 (4, 1) 1 (4, 1)1 22 (3, 1) 1 (3, 1) 1 23 (8, 1) 1 24 (7, 1) 1 25 (6, 1) 1 26 (1, 1) 127 (0, 1) 1

A number of CSI-RS configurations may be used in one cell, wherein apower CSI-RS may use zero or one configuration, and a zero-power CSI-RSmay use zero or several configurations.

In case of the zero-power CSI-RS, in Table 1, 16 configuration types of4 ports may be represented in 16-bit bitmap, and various configurationsmay be made with each bit set as 1. The bitmap is indicated byZeroPowerCSI-RS of an upper layer. However, an RE is excluded which isset as a non-zero power CSI-RS. The MSB (most significant bit) is alowest CSI-RS configuration index and an ascending-order configurationindex is represented in order of the bit

In the following case, the terminal is assumed not to transmit a CSI-RS.

In a special subframe in FS type2

In a subframe where CSI-RS collides with synchronization signals, PBCH,and SystemInformationBlockType1 messages

In a subframe where a paging message is transmitted.

In set

S,

such as

S={15},

S={15,16},

S={17,18},

S={19,20}

or

S={21,22},

an RE (Resource Element) where a CSI-RS of one antenna port istransmitted is not used for transmission of a PDSCH or a CSI-RS ofanother antenna port.

The subframe configuration

I_(CSI-RS)

of a CSI-RS is indicated by an upper layer, and as in Table 3, thesubframe configuration of the CSI-RS and the subframe offset value areindicated.

TABLE 3 CSI-RS SubframeConfig CSI-RS periodicity CSI-RS Subframe offsetICSI-RS TCSI-RS (subframe) ICSI-RS (subframe) 0-4 5 ICSI-RS  5-14 10ICSI-RS-5 15-34 20 ICSI-RS-15 35-74 40 ICSI-RS-35  75-154 80 ICSI-RS-75

The following Table 4 represents CSI-RS configuration IE (Informationelement)

TABLE 4 --ASN1START CSI-RS-Config-r10 ::= SEQUENCE{    csi-RS-r10CHOICE{     release NULL,     setup  SEQUENCE{      antennaPortsCount-r10 ENUMERATED{an1, an2, an4, an8},      resourceConfig-r10 INTEGER(0..31),       subframeConfig-r1INTEGER(0..154),       p-C-r10 INTEGER(−8..15)       }    }   OPTIONAL, -- Need ON    zeroTxPowerCSI-RS-r10  CHOICE{       release NULL,      setup SEQUENCE{          zeroTxPowerResourceConfigList-r10 BITSTRING(SIZE(16)),          zeroTxPowerSubframeConfig-r10 INTEGER(0..154)      }    } }  OPTIONAL  -- Need ON --ASN1STOP

The CSI-RS configuration IE (information element) is CSI-RS-Config-r10information and may include information on antennaPortsCount,resourceConfig, subframeConfig, and p-C-r10 as parameters forconfiguring a CSI-RS which is a reference signal. Further, the CSI-RSconfiguration IE may include a plurality of parameters inzeroTxPower-RS-r10 as parameters for configuring muted CSI-RS(zero-power CSI-RS).

That is, the CSI-RS configuration IE (information element) may includeinformation on the configuration of zero-power CSI-RS and CSI-RS.

The parameters included in the configuration IE may include informationdisclosed in Table 5 as follows.

TABLE 5 CSI-RS-Config field description antennaPortsCount Parameterrepresents the number of antenna ports used for transmission of CSIreference signals where an1 corresponds to 1, an2 to 2 antenna portsetc. see TS 36.211[1, 6.10.5]. p-C Parameter: Pc, see TS 36.213[2,7.2.5] resourceConfig Parameter: CSI reference signal configuration, seeTS 36.211 [1, table 6.10.5.2-1 and 6.10.5.2-2] subframeConfig Parameter:ICSI-RS, see TS 36.211[1, table 6.10.5.3-1]zeroTxPowerResourceConfigList Parameter: ZeroPowerCSI-RS, see TS36.211[1, 6.10.5.2] zeroTxPowerSubframeConfig Parameter: ICSI-RS, see TS36.211[1, table 6.10.5.3-1]

FIG. 5 is a conceptual view illustrating a data transmission methodusing CoMP (coordinated multipoint transmission).

The CoMP means a cooperative communication scheme between points. In amulti-cell multi-distributed node system, the CoMP may apply to reduceinter-cell interference, and in a single cell multi-distributed nodesystem, intra-cell inter-point interference may be reduced. If using theCoMP, the terminal may be jointly supported by multiple nodes. In casethe CoMP is used, each base station may support one or more terminals atthe same time using the same radio frequency resource so as to enhancesystem performance. Further, when using the CoMP, the base station mayperform the space division multiple access (SDMA) scheme based on thestate information on the channel between the base station and theterminal.

A primary purpose of CoMP is to enhance communication performance ofterminals positioned at a cell boundary or at a node boundary. In LTE,CoMP schemes may be generally divided into the following two typesdepending on the data transmission scheme.

Joint Processing (JP)

FIG. 5(A) illustrates joint processing (JP). Referring to FIG. 5(A),joint processing (JP) refers to a scheme of transmitting data for theterminal 50 with the data shared by one or more nodes 510 and 520.

Joint processing (JP) may be classified into three types depending onthe transmission method: coherent Joint Transmission, Non-Coherent JointTransmission and Dynamic Point (Cell) Selection. The coherent jointtransmission refers to a method of simultaneously processing datareceived from the terminal 500 by using precoding between cells. Thenon-coherent joint transmission refers to a method of the terminal 500receiving and processing an OFDM signal using soft-combining.

In DPS (dynamic point selection), among a plurality of cells, one cell(or node 510) is in charge of data transmission through the PDSCH(physical downlink shared channel) and another cell (or another node520) may transmit data to the terminal using a method of removinginterference through muting. In case of using DPS, transmitting/mutingpoint (node) may change when in one subframe another subframe istransmitted or with respect to the resource block pair in one frame.

(2) Coordination Scheduling (CS)/Coordination Beamforming (CB)

FIG. 5(B) illustrates coordination scheduling (CS)/coordinationbeamforming (CB). Referring to FIG. 5(B), CS/CB refers to a method inwhich transmission to the terminal 550 may be done from only one node(serving point, 560), and another node 570 cooperates with the servingpoint in such a manner as reducing interference with respect toscheduling or transmission beams. Further, the CS/CB may use an SSPS(Semi-static point selection) scheme. The SSPS represents that aspecific terminal 550 receives transmission from one point (or node orcell, 560) and the transmission point transmitting data to the terminalis changed only in a semi-static way.

FIG. 6 is a conceptual view illustrating a newly introduced controlchannel, e-PDCCH (enhanced physical downlink control channel).

An introduction to a multi-distributed node system, such as RRH (radioremote head), enables application of various communication schemes, suchas cooperation of each terminal/base station or cooperative scheme, sothat link quality may be enhanced. Various communication schemes, suchas MIMO (multiple-input multiple-output) and cooperative communication(for example, CoMP (Coordinated Multi-Point transmission/reception)),have limitations in applying through current control channels to amulti-distributed node environment including a plurality of nodes.

Accordingly, a need for introduction to a new control channel existswhich may apply to the multi-distributed node environment. A new controlchannel defined according to such needs is e-PDCCH (RRH-PDCCH andx-PDCCH are collectively referred to as e-PDCCH). In the subframe, as aposition where the e-PDCCH 600 is assigned, rather than the existingcontrol region (hereinafter, referred to as “PDCCH region”), a datatransmission region (hereinafter, referred to as “PDSCH (physicaldownlink shared channel)) may be used.

Control information for the node of the multi-distributed node systemmay be transmitted per terminal through e-PDCCH 600, and thus, anyproblem that arises due to lack of the control region may be addressed.The terminal should perform a blind decoding procedure to detect whetherthere is e-PDCCH 600. e-PDCCH 600 performs the same scheduling operation(PDSCH, PUSCH control) as the existing PDCCH, but as the number ofterminals connected to the node (for example, RRH (remote radio head)increases, more e-PDCCHs 600 may be assigned in the PDSCH region, whichleads to an increase in count of blind decoding which should be done bythe terminal, so that complexity may be increased.

A specific method of assigning e-PDCCH 600 may be defined based on thestructure of R-PDCCH which is a control region newly defined forexisting transmission using a relay.

FIG. 7 is a conceptual view illustrating a relay scheme suggested inLTE.

Referring to FIG. 7, an R-PDCCH (relay physical downlink controlchannel) may be newly defined and used for a decode-and-forward schemeusing the relay 750.

A link between the relay 750 and the base station 700, i.e., backhaullink, and an access link between the relay 750 and the terminal 730 maybe formed in the same frequency spectrum. In case the backhaul link andthe access link are formed in the same frequency spectrum, when therelay 750 receives data from the base station 700 through the backhaullink, the operation in which the relay 750 transmits data to theterminal 730 through the access link may not occur at the same time.Accordingly, there is a need for a method of separating the two linksfrom each other in operation so that transmission and reception are notsimultaneously performed through the backhaul link and the access link.

When a frame is transmitted from the relay 750 to the terminal 730through the access link to separate the backhaul link and the accesslink from each other in operation, a transmission gap is created betweena subframe and another subframe, so that a frame may be transmitted fromthe base station 700 to the relay 750 through the backhaul link in thetransmission gap.

In case of a frame transmitted from the base station 700 to the relay750 through the transmission gap, since the transmission duration isshorter than the full subframe duration, L1/L2 control signal may not betransmitted from the base station 700 to the relay 750 using the generalPDCCH. For such a reason, an R-PDCCH is newly defined and used, which isa relay-specific control channel, in the existing control channel.

FIG. 8 is a conceptual view illustrating a structure of allocation of anR-PDCCH for a relay.

Referring to FIG. 8, R-PDCCH uses the same format as a DCI format usedfor PDCCH, and may transmit downlink scheduling assignment 800 anduplink scheduling grants 850. In general, as a method of splitting aframe into a control region and a data region, in light of latency, thecontrol regions needs to be positioned at the foremost portion of thesubframe as possible.

For the same reason, the downlink scheduling assignment 800 of theR-PDCCH may be first assigned to the first slot of the subframe. Theuplink scheduling grant 850, which is relatively less critical in lightof latency, may be assigned to the second slot of the subframe. Further,the R-PDCCH is configured so that a resource element used for R-PDCCH isspanned in a small range over the frequency axis and in a large rangeover the time axis in terms of overhead and scheduling flexibility.

When using such structure of R-PDCCH, the terminal may first decode thetime-critical downlink scheduling assignment 800. If there is no uplinkscheduling grant 850, the resource element where the uplink schedulinggrant 850 may be used for transmitting the PDSCH.

The regions other than R-PDCCH, CRS (cell-specific reference signal),DMRS (demodulation reference signal) may be used to transmit PDSCH(physical downlink shared channel). The method of transmitting the PDSCHmay be determined depending on a reference signal through which thetransmission mode, DCI format, and R-PDCCH are demodulated.

The following Table 6 shows a method of transmitting PDSCH according totransmission mode, DCI format, and R-PDCCH.

TABLE 6 Transmission Transmission scheme of mode DCI format PDSCHcorresponding to R-PDCCH Mode 8 DCI format If the R-PDCCH is demodulatedbased on 1A UE-specific reference signals: Single antenna port; port 7and n_(SCID) = 0 is used. If the R-PDCCH is demodulated based oncell-specific reference signals: If the number of PBCH antenna ports isone: Single-antenna port, port 0 is used Otherwise Transmit diversity isused DCI format Dual layer transmission, port 7 and 8; or 2Bsingle-antenna port, port 7 or 8 Mode 9 DCI format If the R-PDCCH isdemodulated based on 1A UE-specific reference signals: Single antennaport; port 7 and n_(SCID) = 0 is used. If the R-PDCCH is demodulatedbased on cell-specific reference signals: If the number of PBCH antennaports is one: Single-antenna port, port 0 is used Otherwise Transmitdiversity is used DCI format Up to 4 layer transmission, ports 7-10 2C

Referring to Table 6, the method of transmitting PDSCH may be determineddepending on whether DM-RS or CRS is used for demodulation oftransmission mode, DCI format, and R-PDCCH.

The transmission mode concerns which multi-antenna transmission schemeis to be used, and the transmission method according to eachtransmission mode may be as follows:

Transmission mode 1: Single-antenna transmission.

Transmission mode 2: Transmit diversity.

Transmission mode 3: Open-loop codebook-based precoding in the case ofmore than one layer, transmit diversity in the case of rank-onetransmission.

Transmission mode 4: Closed-loop codebook-based precoding.

Transmission mode 5: Multi-user-MIMO version of transmission mode 4.

Transmission mode 6: Special case of closed-loop codebook-basedprecoding limited to single-layer transmission.

Transmission mode 7: Release-8 non-codebook-based precoding supportingonly single-layer transmission.

Transmission mode 8: Release-9 non-codebook-based precoding supportingup to two layers.

Transmission mode 9: Release-10 non-codebook-based precoding supportingup to eight layers.

As a transmission mode to transmit R-PDCCH, transmission mode 8 andtransmission mode 9 may be used.

DCI (downlink control information) may have a plurality of formats, andamong the plurality of DCI formats, the DCI format used for transmissionof PDSCH may have DCI format 1A and DCI format 2B in case oftransmission mode 8, and may have DCI format 1A and DCI format 2C incase of transmission mode 9. The details on various DCI formats arespecified in 3GPP TS 36.213 V10.3.0 “3rd Generation Partnership ProjectTechnical Specification Group Radio Access Network; Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical layer procedures (Release10)”.

For example, in case transmission mode 8, DCI format is 1A, and thereference signal used for demodulating R-PDCCH is UE-specific referencesignal (DM-RS), a single antenna (port 7) is used and 0 is used asscrambling ID (SCID) to transmit the PDSCH. In contrast, in case thereference signal used for demodulation of R-PDCCH is CRS, only when thenumber of PBCHs (physical broadcast channel) transmission antennas is 1,port 0 is used, and when the number of PBCH transmission antennas is 2or 4, a shift to Tx diversity mode is made to use all of ports 0 to 1and ports 0 to 3.

FIGS. 9 and 10 are conceptual views illustrating methods of assigninge-PDCCH in the subframe.

e-PDCCH may be a channel that transmits control information demodulatedby DM (demodulation)-RS (reference signal) transmitted in the resourceregion where e-PDCCH is transmitted.

Referring to FIG. 9, e-PDCCH may be configured in both 1st slot 910 and2nd slot 920, and DL grant (downlink scheduling assignment, 950) may beassigned to the first slot 910 and UL grant (uplink scheduling grant,960) may be assigned to the second slot 920. Here, the DL grant 950 maymean DCI formats (e.g., DCI formats 1, 1A, 1B, 1C, 1D, 2, and 2A) fortransmitting downlink control information of the terminal and the ULgrant 960 may mean DCI formats (e.g., DCI formats 0 and 4) which areuplink control information of the terminal.

Since the DL grant 950 and the UL grant 960 are separately transmittedfor each of the slots 910 and 920 in the subframe, the terminal mayconfigure s search space in the first slot 910 in the subframe toperform blind decoding to find the DL grant 950 and may perform blinddecoding to find the UL grant 960 in the search space configured in thesecond slot 920 in the subframe, thereby demodulating the DL grant 950and the UL grant 960.

Referring to FIG. 10, assuming that e-PDCCH is configured only in thefirst slot 1010 in the subframe when assigning e-PDCCH, DL grant(downlink scheduling assignment, 1050) and UL grant (uplink schedulinggrant, 1060) may be simultaneously assigned to the first slot 1010 inthe subframe. Accordingly, the DL grant 1050 and the UL grant 1060 aresimultaneously present in e-PDCCH of the first slot 1010, and theterminal may perform blind decoding to find the DL grant 1050 and the ULgrant 1060 only in the first slot 1010 of the subframe.

In the general radio communication standards, the physical cell ID (PCI)that is information regarding which cell the current terminal ispositioned may be transmitted to the terminal when the synchronizationsignal (SS) is transmitted from the base station to the terminal. ThePCI transmitted to the terminal is specified to be used to receivevarious PHY channels or signals (e.g. PBCH, PDCCH, PCFICH, downlinkRS(CRS, CSI-RS, DM-RS, PRS) in LTE-A) or to transmit the PHY channels orsignals (e.g. PUCCH4 uplink RS(SRS, DM-RS) in LTE-A) (in IEEE802.16m,DRU permutation rule is determined by PCI).

Nested virtual cell system (NVCS) means a system that configures a cellID (or virtual cell ID: VCI) associated with generation of some physicalsignals used for transmission/reception by some nodes in the cell in thesingle cell multi-distributed node system to be different from PCI (orPCI used in primary & secondary SS) commonly used by all the nodes inthe cell.

Hereinafter, in some embodiments of the present invention, a cell IDassociated with generation of some physical signals used fortransmission/reception by some nodes in the cell in the single cellmulti-distributed node system is defined as a virtual cell ID.

FIG. 11 is a conceptual view illustrating the nested virtual cellsystem.

Referring to FIG. 11, all of the six nodes 1110, 1120, 1130, 1140, 1150,and 1160 are positioned in cell A 1100. Each node uses the primary SS(synchronization signal) and secondary SS generated with common PCI ‘A’which is the physical cell ID (PCI) of cell A 1100. Accordingly, whenthe terminal enters the nested virtual cell system, the terminals 1180and 1190 recognize that they are currently in the cell A 1100irrespective of the relative position between the terminal and the node.In such case, the terminals 1180 and 1190 cannot perform the operation,such as cell selection/re-selection or handover, which is the operationdefined among the existing nodes between nodes belonging to cell A 1100.

However, in the multi-distributed node system, the operation definedbetween cells needs to be newly defined and used between the nodesincluded in one cell. Accordingly, the six nodes 1110, 1120, 1130, 1140,1150, and 1160 included in the same cell A 1100 may use differentvirtual cell IDs so that the operation performed between cells may bealso done between the nodes 1110, 1120, 1130, 1140, 1150, and 1160.

As shown in FIG. 11, six nodes node B to node G 1110, 1120, 1130, 1140,1150, and 1160 may be included in cell A 1100, and each node may use avirtual cell ID to generate some physical signals (e.g., CSI-RS) and maytransmit the generated physical signals to the terminals 1180 and 1190.For example, in case a virtual cell ID is used to indicate a nodeassociated with generation of the CSI-RS, the base station sends arequest for CSI (channel state information) feedback for a specific nodeto the terminal 1180 while informing the virtual channel ID used by thecorresponding node to the terminal. In case the base station intends tobe aware of the channel state between the terminal and node ‘B’ 1110,the base station may send a request for CSI (channel state information)feedback for the node 1110 having virtual cell ID ‘B’ to the terminal1180.

Likewise, when sending a request for CSI feedback for the nodes 1140 and1150 that are to attend CoMP to the terminal 1190 so as to perform CoMPtransmission to the terminal 1190, virtual cell IDs E and F for thenodes to attend CoMP (CoMP measurement set or CoMP reporting set, 1140,1150 may be specified and notified to the terminal 1190.

For example, in case the node 1140 and the node 1150 perform CoMP on theterminal 1190, the base station may transmit indication information onthe nodes performing CoMP, i.e., virtual cell ID ‘E’ and virtual cell ID‘F’, to the terminal 1190. Various node-based operations as well astransmission using CoMP may be performed based on the virtual cell ID ofeach node.

For example, when the base station transmits a specific signal separatedfor each node 1110, 1120, 1130, 1140, 1150, and 1160 to the terminal andis fed back with a measurement value in response in order to figure outwhich node 1110, 1120, 1130, 1140, 1150, and 1160 the terminals 1180 and1190 are around, the virtual cell Id used for each node 1110, 1120,1130, 1140, 1150, and 1160 needs to be notified to the terminals 1180and 1190.

That is, the operation between each node and the terminal may be definedbased on the virtual cell ID defined based on the node in themulti-distributed node system. In an embodiment of the presentinvention, the operation between the terminal and the node based on thevirtual cell ID as follows is disclosed.

Method of transmitting node information used for generating CSI-RS inthe multi-distributed node system by adding virtual cell ID informationto CSI-RS information element

Method of transmitting e-PDCCH setting information through an RRCmessage from a base station to a terminal in the multi-distributed nodesystem, with PPCI (primary physical cell ID) included in the settinginformation

Method of implicitly or explicitly transmitting a primary physical cellID through a configuration information element of CSI-RS transmittedfrom a node to a terminal in the multi-distributed node system

Method of performing e-PDCCH demodulation, PDSCH demodulation,UE-specific RS demodulation, serving point indication for CoMP based onvirtual cell ID information of the primary CSI-RS configured by a basestation in the multi-distributed node system and transmitted through anode

Hereinafter, in an embodiment of the present invention, for ease ofdescription, a multi-distributed node system is assumed. However, theembodiment of the present invention may also apply to when a terminalreceives data from a plurality of nodes or a plurality of base stations,like the CoMP of the multi-cell system, and such embodiment is alsowithin the scope of the present invention.

Hereinafter, the embodiment of the present invention discloses a methodof using an RRC message, such as PhysicalConfigDedicated IE and CSI-RSconfiguration or e-PDCCH setting information, so that a base stationtransmits virtual cell ID of a node, primary physical cell ID, andprimary CSI-RS to the terminal. However, other transmission formats thanthe RRC message may be used for the base station to transmit the virtualcell ID of the node, primary physical cell ID, and primary CSI-RS to theterminal, and such embodiment is also included in the scope of thepresent invention.

FIG. 12 is a conceptual view illustrating a method of transmitting avirtual cell ID through a CSI-RS information element according to anembodiment of the present invention.

Referring to FIG. 12, in the multi-distributed node system, a pluralityof nodes 1210, 1220, 1230, 1240, 1250, and 1260 may be present in onebase station 1200. The terminal 1280 may receive a CSI-RS from at leastone node present in the multi-distributed node system.

For example, the terminal 1280 may receive a CSI-RS from at least onenode among nodes 1210 and 1220. The terminal may recognize one of thenodes 1210 and 1220 from which the received CSI-RS has been transmittedbased on the virtual cell ID information included in the received CSI-RSconfiguration information element (CSI information element, CSI-RS IE orCSI-RS configuration information also have the same meaning).

The following Table 7 shows CSI-RS configuration information elementsthat include virtual cell ID information.

TABLE 7    CSI-RS-Config IE    {    csi-RS // (OPTIONAL)    {      Antenna port : select one of 1, 2, 4, and 8,       resourceconfiguration : select one of integers 0~31    subframe configuration :select one of integers 0~154,       Power control : select one ofintegers −8 ~ 15       Cell ID : select one of integers 0~503 (optional:omitted in such case as PCI through SS)    }    zeroTxPowerCSI-RS//(OPTIONAL)    {       zeroTxPowerResourceConfigList : 16 bit°| bitmap,      zeroTxPowerSubframeConfig : select one of integers 0~154    }    }

Referring to Table 7, the cell ID field including virtual cell IDinformation may be added to CSI-RS configuration information element (orCSI information element, CSI IE). The terminal 1280 may be aware of oneof the nodes 1210 and 1220 from which the received CSI-RS is transmittedbased on the cell ID field. For example, based on the cell ID field ofthe CSI-RS information element, the terminal 1280 may be aware that thereceived CSI-RS has been transmitted from the node 1220. In such case,the terminal 1280 may feed channel information between the terminal 1280and the node 1220 back to the node 1220 based on the virtual cell IDinformation. As another example, the terminal may obtain channelinformation per node based on the virtual cell ID informationtransmitted from nodes upon performing CoMP.

The cell ID field shown in Table 7 is an example of a field fortransmitting the virtual cell ID of the node and may be defined in otherways. For example, it may be replaced by PhysCellId IE, which is defined“3GPP TS 36.331 V10.2.0: “Evolved Universal Terrestrial Radio Access(E-UTRA); Radio Resource Control (RRC); Protocol specification (Release10)” or a new cell id IE may be defined (e.g., virtual cell id).

In case the virtual cell ID transmitted through the cell ID is the sameas physical cell ID (PCI) sent through the synchronization signal (SS),the virtual cell ID information transmitted through the cell ID fieldmay not be transmitted. In such case, the operation based on theabove-described virtual cell ID may be performed using the existing PCIvalue.

FIG. 13 is a conceptual view illustrating a method of transmittingvirtual cell ID information that transmits e-PDCCH according to anembodiment of the present invention.

In a single cell multi-distributed node system, due to lack of controlchannel, introduction to e-PDCCH is considered. e-PDCCH may includeterminal specific control information, and unlike the existing PDCCH,the control information transmitted through e-PDCCH may be used as areference signal for demodulating UE-specific RS (or DM(demodulation)-RS) instead of cell-specific RS.

In a single cell multi-distributed node system, each node may transmitcontrol information to different terminals through e-PDCCH. That is, incase the multi-distributed node system operates as an NVCS (nestedvirtual cell system), the operation of a plurality of nodes 1310, 1320,1330, 1340, 1350, and 1360 in a cell may be discerned based on virtualcell ID. Each node may transmit individual control information to theterminal 1380 through e-PDCCH based on the virtual cell ID.

The base station 1300 may transmit PPCI (primary physical cell ID) tothe terminal 1380 using a transmission format, such as an RRC message.PPCI (primary physical cell ID) is information indicating a node thattransmits data which is supposed to be received by the terminal 1380 andmay be used to discern a node that transmits control informationsupposed to be received by the terminal through e-PDCCH.

The terminal 1380 may be aware of a node from which to receive controlinformation based on the PPCI. Hereinafter, according to an embodimentof the present invention, a method of a terminal receiving controlinformation transmitted from a specific node through e-PDCCH based onthe configuration information of the e-PDCCH transmitted from the basestation 1300 is described.

To transmit a primary physical cell ID, the base station 1300 may use,for example, RRC message. Hereinafter, according to an embodiment of thepresent invention, as the RRC message, CSI-RS configuration element ore-PDCCH configuration information, PhysicalConfigDedicated IE are used,but are not limited thereto, and other RRC messages may be also used.Further, the RRC message used to transmit the primary physical cell IDis an example, and the primary physical cell ID may be transmitted byother transmission methods.

Referring to FIG. 13, in a multi-distributed node system, a plurality ofnodes 1310, 1320, 1330, 1340, 1350, and 1360 may be present in one basestation 1300. The terminal 1380 may receive control information throughe-PDCCH from at least one node present in the multi-distributed nodesystem.

To determine a node from which the control information received throughat least one e-PDCCH is transmitted, the terminal 1380 may use PPCI. Theterminal may receive control information through e-PDCCH transmittedfrom a node corresponding to PPCI.

The base station 1300 may transmit PPCI (primary physical cell ID) tothe terminal 1380 using the following methods:

1) method of transmitting PPCI from the base station 1300 to theterminal 1380, with a predetermined message (e.g., RRC message) forconfiguring e-PDCCH included in the PPCI

2) method of explicitly or implicitly indicating PPCI to the terminalthrough CSI-RS transmitted from the node

Firstly, the method of transmitting PPCI from the base station 1300 tothe terminal 1380, with a predetermined message (e.g., RRC message) forconfiguring e-PDCCH included in the PPCI is described. Controlinformation may be transmitted through e-PDCCH from a plurality of nodes1310, 1320, and 1330 having different virtual cell IDs to the terminal1380. In such case, the terminal 1380 may determine a node from whichthe control information received through e-PDCCH has been transmittedbased on PPCI. The terminal 1380 may receive control informationtransmitted from a node having the same virtual cell ID as PPCI (primaryphysical cell ID).

Such PPCI may be transmitted from the base station 1300 to the terminal1380. For example, the base station 1300 may transmit PPCI to theterminal 1380 using an RRC message used to transmit e-PDCCHconfiguration information, such as whether e-PDCCH is subjected tointerleaving, search space position information, or search space sizeinformation. That is, the configuration information of e-PDCCH may betransmitted to the terminal, with the PPCI field, which is nodeinformation, included in the configuration information of e-PDCCH.

Next, the method of explicitly or implicitly indicating PPCI to theterminal through CSI-RS transmitted from the node may be used, and thefollowing two methods may be adopted. The CSI-RS used to indicate PPCImay be referred to as primary CSI-RS.

Method of adding a new field (e.g., indication of primary PCI) to CSI-RSconfiguration information element to explicitly indicate to the terminalCSI-RS having the same virtual cell ID as PPCI

Method of the terminal implicitly estimating the virtual cell ID of theCSI-RS with PPCI based on the CSI-RS positioned at a specific positionamong a plurality of CSI-RSs received to the terminal

The method of adding a new field (e.g., indication of primary PCI) toCSI-RS configuration information element to explicitly indicate to theterminal CSI-RS having the same virtual cell ID as PPCI may betransmitted to RRC message through CSI-RS configuration informationelement as in, e.g., Table 8 below.

The following Table 8 shows a method of transmitting PPCI to a pluralityof terminals through CSI-RS configuration IE.

TABLE 8    CSI-RS-Config IE    {    for (allocation of multiple csi-RSpatterns) {      csi-RS // (OPTIONAL)      {         Antenna port :select one of 1, 2, 4, and 8,         resource configuration : selectone of integers 0~31,         subframe configuration : select one ofintegers 0~154,         Power control :select one of integers −8 ~ 15        Cell ID : select one of integers 0~503 (optional: omitted insuch case as PCI through SS)         Indication of primary PCI: On/Off(Optional: only when the cell ID is PPCI, this field is ON. If the cellID field is present only for one CSI-RS resource, this field may be notremoved)       }    }    }

Referring to Table 8, the base station 1300 may transmit information ona plurality of CSI-RS patterns to the terminal 1380 through CSI-RSconfiguration IE. The CSI-RS patterns may be used to distinguish CSI-RSstransmitted through different virtual cell IDs from each other, andCSI-RS configuration information element may be set for each CSI-RSpattern.

For example, in case CSI-RSs are transmitted from nodes 1310 and 1320,respectively, information on each node that has transmitted the CSI-RSmay be indicated based on the cell ID field of the transmitted CSI-RSconfiguration information element. Further, it may be known through theindication of primary PCI which node corresponds to the primary physicalcell ID. For example, in case CSI-RS configuration information elementis received from each of nodes 1310 and 1320 and the indication ofprimary PCI field of the CSI-RS configuration information elementtransmitted from node 1310 is on, the PPCI of the terminal 1380 may bethe node 1310, and the terminal 1380 may receive control informationthrough e-PDCCH transmitted from the node 1310.

As another example, in case the nodes 1310 and 1320 perform transmissionusing CoMP, a plurality of CSI-RSs having different virtual cell IDs, asreference signals used by different nodes, may be transmitted over onesubframe. In such case, a plurality of CSI-RS patterns may be configuredthrough CSI-RS configuration information of the RRC message.

The terminal 1380 may be aware of the virtual cell ID information of theplurality of CSI-RSs received based on the CSI-RS configurationinformation. That is, it may catch the virtual cell ID information ofthe received CSI-RS based on the cell ID field included in the CSI-RSconfiguration IE of Table 2. Further, it may be provided to the terminal1380 the virtual cell ID of which CSI-RS is the same as the primaryphysical cell ID based on the indication of primary PCI included in theCSI-RS configuration information.

The terminal 1380 may perform one of the following operations todetermine PPCI for receiving e-PDCCH based on the received CSI-RSconfiguration information element.

In case a plurality of cell ID fields are present in the CSI-RSconfiguration information element, e-PDCCH may be received from a nodehaving the virtual cell ID value indicated as PPCI by the indication ofprimary PCI.

In case only one cell ID field is present in the CSI-RS configurationinformation element, e-PDCCH may be received from a node having thecorresponding virtual cell ID. In such case, an indication of primaryPCI field is not required to be provided, which indicates which cell IDis PPCI.

If no cell ID field is present in the CSI-RS configuration informationelement, e-PDCCH may be received based on the physical cell ID (PCI)obtained through SS.

For example, in case the terminal 1380 receives a plurality of CSI-RSshaving different virtual cell IDs, the terminal may determine whichvirtual cell ID is the primary physical cell ID based on the indicationof primary PCI of the configuration information element of CSI-RS whichis the RRC message. The terminal 1380 may receive control informationthrough e-PDCCH transmitted from a node having the virtual cell IDcorresponding to the primary physical cell ID produced by configurationinformation element of CSI-RS.

According to another embodiment of the present invention, withoutexplicitly transmitting information on the virtual cell ID through thefield (indication of primary PCI) newly defined in the RRC message as inTable 2, the terminal may implicitly estimate the information on thevirtual cell ID.

FIG. 14 is a conceptual view illustrating a method of allowing aterminal to implicitly estimate information on a virtual cell IDaccording to an embodiment of the present invention.

Referring to FIG. 14, the terminal 1480 may receive a plurality ofCSI-RSs having different virtual cell IDs.

For example, the terminal 1480 may receive a subframe including a firstCSI-RS pattern transmitted from a first node 1410 and a second CSI-RSpattern transmitted from a second node 1420. The CSI-RS pattern meansaggregation of CSI-RSs having specific virtual cell IDs.

The terminal 1480 needs to determine which one of the first and secondnodes 1410 and 1430 corresponds to PPCI. According to an embodiment ofthe present invention, among the CSI-RSs received by the terminal 1480,the virtual cell ID of a CSI-RS transmitted in a specific turn or aCSI-RS positioned at a specific location may be determined as theprimary physical cell ID.

For example, the CSI-RS received by the terminal 1480 may be specifiedas a CSI-RS that is transmitted at a specific time and position in thesubframe based on parameters, such as configuration number and subframeconfiguration number. The virtual cell ID of the specified CSI-RS may bethe primary physical cell ID and the node that has transmitted thecorresponding CSI-RS may be the PPCI. That is, the terminal 1480 mayimplicitly determine the virtual cell ID of the CSI-RS transmitted in aspecific turn or present at a specific position as the PPCI (primaryphysical cell ID) and may receive control information transmitted from anode having the same virtual cell ID through e-PDCCH.

By using such method, even without transmitting a field, such asindication of primary PCI field, for determining whether the virtualcell ID that has transmitted the CSI-RS is PPCI, the primary virtualcell ID may be implicitly estimated that transmits control informationthrough e-PDCCH based on a specific non-zero-power CSI-RS resourceelement(s). At this time, the terminal may perform the followingoperations:

In case a plurality of non-zero-power CSI-RS resources are present inthe CSI-RS configuration, the terminal may receive control informationtransmitted through e-PDCCH from a node corresponding to primaryphysical cell ID by determining that the virtual cell ID of a specificCSI-RS resource is the primary physical cell ID

In case the cell ID field is absent from a specific CSI-RS, the terminalmay receive control information through e-PDCCH based on the physicalcell ID obtained through SS.

In case only one non-zero-power CSI-RS resource is present in the CSI-RSconfiguration, the terminal may receive control information transmittedthrough e-PDCCH based on the virtual cell ID produced based on thereceived one non-zero-power CSI-RS. If the cell ID field of the receivednon-zero-power CSI-RS is omitted, e-PDCCH may be received based on thephysical cell ID obtained through SS.

According to an embodiment of the present invention, upon configuringCSI-RS to be transmitted from a base station to a terminal, primaryCSI-RS resource for producing PPCI (primary physical cell ID) may beindicated.

FIG. 15 is a conceptual view illustrating a method of controlling theoperation of a node using PPCI according to an embodiment of the presentinvention.

The primary PCI (PPCI) may be used for other purposes as well as fordemodulation of e-PDCCH.

For example, it may be assumed as in Table 8 that a terminal receives aplurality of CSI-RS patterns having different virtual cell IDs. Whenconfiguring the CSI-RS to be transmitted to the terminal 1580, the basestation 150 may indicate a primary CSI-RS to produce the PPCI.

The terminal 1580 may obtain various types of information based on theprimary PCI indicated by the base station 1500. For example,

Primary CSI-RS may be used for indicating a serving point in the CoMPoperation. For example, the terminal 1580 may be provided withinformation stating that the node 1510 having the virtual cell IDindicated by the cell ID of the primary CSI-RS upon performing the CoMPoperation is the serving point based on the primary CSI-RS. It maydistinguish the serving point from the remaining coordinating point(s)based on the virtual cell ID information indicated by the cell ID of theprimary CSI-RS in the CoMP feedback. For example, to support the CS/CB(coordinated scheduling/beamforming) operation, it needs to be discernedwhich node is a node (serving point, 1510) which transmits data andwhich node is a node (coordinating points, 1520) to reduce damage frominterference. At this time, the terminal 1580 may configure feedbackassuming that the CSI-RS resource indicated as PPCI is CSI-RStransmission from the serving point 1510.

PPCI may be used for PDSCH demodulation of the terminal. The basestation 1500 generates PDSCH with PPCI (used for generating sequence)and transmits it to the terminal 1580 irrespective of whether the nodeactually transmits data. The terminal 1580 may perform PDSCHdemodulation when PPCI used for generating PDSCH is same as terminal'sPPCI. The terminal 1580 may also perform UE-specific RS demodulationbased on PPCI. The base station 1500 generates UE-specific RS with PPCIand transmits it to the terminal 1580 irrespective of whether the nodeactually transmits data. The terminal 1580 may perform UE-specific RSdemodulation when PPCI used for generating UE-specific RS is same asterminal's PPCI.

Specific parameters (e.g., cell ID field) for the primary CSI-RS mayapply not only to CSI-RS-configuration information element but also toother information elements, and thus may be defined in the messageformat higher than the CSI-RS-configuration information element and maybe then transmitted.

The following Table 9 shows that a primary cell ID field is added toPhysicalConfigDedicated IE which is an IE (information element) toperform UE specific physical channel configuration.

TABLE 9 PhysicalConfigDedicated ::= SEQUENCE { Primary cell IDINTEGER(0..503) OPTIONAL pdsch-ConfigDedicated PDSCH-ConfigDedicatedOPTIONAL,-- Need ON pucch-ConfigDedicated PUCCH-ConfigDedicatedOPTIONAL,-- Need ON pusch-ConfigDedicated PUSCH-ConfigDedicatedOPTIONAL,-- Need ON uplinkPowerControlDedicatedUplinkPowerControlDedicated OPTIONAL,    -- Need ONtpc-PDCCH-ConfigPUCCH TPC-PDCCH-Config OPTIONAL,-- Need ONtpc-PDCCH-ConfigPUSCH TPC-PDCCH-Config OPTIONAL,-- Need ONcqi-ReportConfig CQI-ReportConfig OPTIONAL,--Cond CQI-r8soundingRS-UL-ConfigDedicated SoundingRS-UL-ConfigDedicated    OPTIONAL,-- Need ON    antennaInfo CHOICE { explicitValue AntennaInfoDedicated,defaultValue NULL    } OPTIONAL, -- Cond AI-r8 schedulingRequestConfigSchedulingRequestConfig OPTIONAL, -- Need ON    ...,[[cqi-ReportConfig-v920 CQI-ReportConfig-v920 OPTIONAL,--Cond CQI-r8antennaInfo-v920 AntennaInfoDedicated-v920 OPTIONAL-- Cond AI-r8    ]],   [[ antennaInfo-r10 CHOICE { explicitValue-r10AntennaInfoDedicated-r10, defaultValue NULL } OPTIONAL, -- Cond AI-r10antennaInfoUL-r10 AntennaInfoUL-r10 OPTIONAL,-- Need ON cif-Presence-r10BOOLEAN OPTIONAL,-- Need ON cqi-ReportConfig-r10 CQI-ReportConfig-r10OPTIONAL,-- Cond CQI-r10 csi-RS-Config-r10 CSI-RS-Config-r10 OPTIONAL,--Need ON pucch-ConfigDedicated-v1020 PUCCH-ConfigDedicated-v1020   OPTIONAL, -- Need ON pusch-ConfigDedicated-v1020PUSCH-ConfigDedicated-v1020    OPTIONAL, -- Need ONschedulingRequestConfig-v1020 SchedulingRequestConfig-v1020    OPTIONAL,-- Need ON soundingRS-UL-ConfigDedicated-v1020SoundingRS-UL-ConfigDedicated-v1020 OPTIONAL,  -- Need ONsoundingRS-UL-ConfigDedicatedAperiodic-r10SoundingRS-UL-ConfigDedicatedAperiodic-r10 OPTIONAL,  -- Need ONuplinkPowerControlDedicated-v1020 UplinkPowerControlDedicated-v1020   OPTIONAL -- Need ON    ]]     }

Referring to Table 9, the primary cell ID field may be used as aparameter that replaces the existing physical cell ID for specificpurposes (e.g., e-PDCCH setting, PDSCH setting, UE-specific RS setting,or serving point indication for CoMP).

That is, according to an embodiment of the present invention,information on the primary physical cell ID may be transmitted to theterminal by using a method of adding the primary cell ID field and/orprimary cell indicator to be used for specific purposes (e.g., e-PDCCHsetting, PDSCH setting, UE-specific RS setting, or serving pointindication for CoMP) to PhysicalConfigDedicated IE.

According to another embodiment of the present invention, in Table 10, aprimary cell indicator may be added which indicates one of a number ofCSI-RS resources, which corresponds to the primary CSI-RS resource,while configuring the CSI-RS resources, instead of the primary cell IDfield. At this time, the cell ID corresponding to the primary CSI-RSresource is PPCI.

TABLE 10 PhysicalConfigDedicated ::= SEQUENCE { Primary cell indicator(0~N−1)  OPTIONAL pdsch-ConfigDedicated PDSCH-ConfigDedicatedOPTIONAL,-- Need ON pucch-ConfigDedicated PUCCH-ConfigDedicatedOPTIONAL,-- Need ON pusch-ConfigDedicated PUSCH-ConfigDedicatedOPTIONAL,-- Need ON uplinkPowerControlDedicatedUplinkPowerControlDedicated OPTIONAL,    -- Need ONtpc-PDCCH-ConfigPUCCH TPC-PDCCH-Config OPTIONAL,-- Need ONtpc-PDCCH-ConfigPUSCH TPC-PDCCH-Config OPTIONAL,-- Need ONcqi-ReportConfig CQI-ReportConfig OPTIONAL,--Cond CQI-r8soundingRS-UL-ConfigDedicated SoundingRS-UL-ConfigDedicated    OPTIONAL,-- Need ON    antennaInfo CHOICE { explicitValue AntennaInfoDedicated,defaultValue NULL    } OPTIONAL, -- Cond AI-r8 schedulingRequestConfigSchedulingRequestConfig OPTIONAL, -- Need ON    ...,[[cqi-ReportConfig-v920 CQI-ReportConfig-v920 OPTIONAL,--Cond CQI-r8antennaInfo-v920 AntennaInfoDedicated-v920 OPTIONAL-- Cond AI-r8 ]],   [[ antennaInfo-r10 CHOICE { explicitValue-r10AntennaInfoDedicated-r10, defaultValue NULL } OPTIONAL, --Cond AI-r10antennaInfoUL-r10 AntennaInfoUL-r10 OPTIONAL,-- Need ON cif-Presence-r10BOOLEAN OPTIONAL,-- Need ON cqi-ReportConfig-r10 CQI-ReportConfig-r10OPTIONAL,-- Cond CQ1-r10 for (allocating N multipleCSI-RS){csi-RS-Config-r10 CSI-RS-Config- r10<-includinig cell IDOPTIONAL,-- Need ON} pucch-ConfigDedicated-v1020PUCCH-ConfigDedicated-v1020    OPTIONAL, -- Need ONpusch-ConfigDedicated-v1020 PUSCH-ConfigDedicated-v1020    OPTIONAL, --Need ON schedulingRequestConfig-v1020 SchedulingRequestConfig-v1020   OPTIONAL, -- Need ON soundingRS-UL-ConfigDedicated-v1020SoundingRS-UL-ConfigDedicated-v1020 OPTIONAL, -- Need ONsoundingRS-UL-ConfigDedicatedAperiodic-r10SoundingRS-UL-ConfigDedicatedAperiodic-r10 OPTIONAL, -- Need ONuplinkPowerControlDedicated-v1020 UplinkPowerControlDedicated-v1020   OPTIONAL -- Need ON    ]]    }

FIG. 16 is a block diagram illustrating a wireless apparatus accordingto an embodiment of the present invention.

The wireless apparatus 70 includes a processor 72, a memory 74, and atransceiver 76. The transceiver 76 transmits/receives a radio signal andhas an IEEE 802.11 physical layer installed therein. The processor 72 isfunctionally connected to the transceiver 76 to implement the IEEE802.11 MAC layer and physical layer. According to an embodiment of thepresent invention, the processor 72 may determine a node from whichcontrol information is to be received over an e-PDCCH (enhanced physicaldownlink control channel) based on information indicating a primaryphysical cell ID (identification) obtained through an RRC (radioresource control) message received through the transceiver 76. Further,the processor 72 may be configured to implement the above-describedembodiments of the present invention, e.g., the operation for producingthe primary physical cell ID.

The processor 72 and/or the transceiver 76 may include ASIC(application-specific integrated circuits), other chipsets, logiccircuits, and/or data processing devices. The memory 74 may include aROM (read-only memory), a RAM (random access memory), a flash memory, amemory card, a storage medium, and/or other storage devices. Whenimplemented in software, the above-described schemes may be embodied inmodules (procedures or functions) that perform the above-describedfunctions. The modules may be stored in the memory 74 and may beexecuted by the processor 72. The memory 74 may be positioned in oroutside the processor 72, and may be connected to the processor 72 bywell-known various means.

The invention claimed is:
 1. A method for receiving a downlink controlchannel in a wireless communication system, the method comprising:receiving, by a user equipment, synchronization signals on a cell;determining, by the user equipment, a physical cell identity of the cellbased on the synchronization signals; performing, by the user equipment,a blind decoding in a first search space on the cell to find a firstPhysical Downlink Control Channel (PDCCH); receiving, by the userequipment, a Radio Resource Control (RRC) message includingconfiguration information on the cell, the configuration informationincluding information on a second search space for monitoring a secondPDCCH and identity information, wherein the information on the secondsearch space includes information on a size of the second search spaceand information on a location of the second search space; and performinga blind decoding in the second search space on the cell to find thesecond PDCCH using the configuration information, wherein the firstPDCCH is demodulated based on the physical cell identity, and whereinthe second PDCCH is demodulated based on the identity informationincluded in the configuration information of the RRC message, instead ofthe physical cell identity determined based on the synchronizationsignals.
 2. The method of claim 1, wherein the first search space andthe second search space are defined in one subframe in the cellconfigured by a plurality of orthogonal frequency division multiplexing(OFDM) symbols, and wherein first OFDM symbols for the first searchspace among the plurality of OFDM symbols precede second OFDM symbolsfor the second search space among the plurality of OFDM symbols.
 3. Themethod of claim 2, wherein the synchronization signals include a primarysynchronization signal and a secondary synchronization signal.
 4. Awireless apparatus configured for receiving a downlink control channelin a wireless communication system, the wireless apparatus comprising: atransceiver configured to receive radio signals; and a processoroperatively coupled with the transceiver and configured to: instruct thetransceiver to receive synchronization signals on a cell; determine aphysical cell identity of the cell based on the synchronization signals;perform a blind decoding in a first search space on the cell to find afirst Physical Downlink Control Channel (PDCCH); instruct thetransceiver to receive a Radio Resource Control (RRC) message includingconfiguration information on the cell, the configuration informationincluding information on a second search space for monitoring a secondPDCCH and identity information, wherein the information on the secondsearch space includes information on a size of the second search spaceand information on a location of the second search space; and perform ablind decoding in the second search space on the cell to find the secondPDCCH using the configuration information, wherein the first PDCCH isdemodulated based on the physical cell identity, and wherein the secondPDCCH is demodulated based on the identity information included inconfiguration information of the RRC message, instead of the physicalcell identity determined based on the synchronization signals.
 5. Thewireless apparatus of claim 4, wherein the first search space and thesecond search space are defined in one subframe in the cell configuredby a plurality of orthogonal frequency division multiplexing (OFDM)symbols, and wherein first OFDM symbols for the first search space amongthe plurality of OFDM symbols precede second OFDM symbols for the secondsearch space among the plurality of OFDM symbols.
 6. The wirelessapparatus of claim 5, wherein the synchronization signals include aprimary synchronization signal and a secondary synchronization signal.7. The method of claim 1, wherein the physical cell identity is used todecode a channel state information-reference signal (CSI-RS) when theRRC message does not further include another identity information todecode the CSI-RS, and wherein the physical cell identity is not used todecode the CSI-RS when the RRC message further includes the anotheridentity information to decode the CSI-RS.
 8. The wireless apparatus ofclaim 4, wherein the physical cell identity is used to decode a channelstate information-reference signal (CSI-RS) when the RRC message doesnot further include another identity information to decode the CSI-RS,and wherein the physical cell identity is not used to decode the CSI-RSwhen the RRC message further includes the another identity informationto decode the CSI-RS.